Dynamic precipitation behavior and recrystallization mechanism during hot deformation of 7E33 aluminum alloy

Abstract

The 7E33 aluminum alloy was engineered through microalloying conventional 7xxx series alloys with Er and Mn. The evolution of its microstructure during hot working directly affects the final product's mechanical properties. The hot deformation behavior of this alloy was investigated under deformation temperatures ranging from 350 °C to 500 °C and strain rates from 0.01 s⁻¹ to 10 s⁻¹ by isothermal compression tests in this study. Furthermore, an in-depth analysis was conducted on the microstructural evolution during the deformation process. The results show that the peak flow stress increased with decreasing deformation temperature and increasing strain rate. The strain-compensated Arrhenius constitutive equation was established based on the true stress-strain curve, demonstrating a correlation coefficient of 0.990 and an average absolute relative error of 3.842 %. Microstructural analysis demonstrated that the high-angle grain boundary (HAGBs) proportion was observed to first increase and then decrease with rising deformation temperature at a strain rate of 0.01 s⁻¹. A maximum HAGBs fraction of 59.4 % was achieved at 400 °C. Some η-phase particles dissolve, some growth from 8 nm to 30 nm at 400 °C. When the temperature increased to 500 °C, η-phase re-precipitation was observed, characterized by an increase in particle number and a reduction in particle size to 3 nm. The pinning effect on dislocations and grain boundaries was significantly enhanced, resulting in a corresponding suppression of dynamic recrystallization. At 10 s⁻¹ and 450 °C, during the hot deformation, dislocations were aggregated to form a “stepped” structure, which could emit dislocations and further form dislocation networks. The dislocation networks ultimately evolve into subgrain boundaries. Furthermore, discontinuous dynamic recrystallization was significantly inhibited by an increase in deformation temperature, while continuous dynamic recrystallization was effectively suppressed by an elevation in strain rate.